Ganged potentiometer



ocuzv, 1910 Emma 3,537,054 Q GANGED POTENTIOMETER Filed .1958' s sheets-sheet;

v INVENTOR EDWARD H. LIVESAY ATTORNEY 0a. 27, 1970 E. H. was 3,531,054

GANGED POTENTIONETER Filed June 1958 I s Sheets Sheot s g iNvEN'roR EDWARD H. LIVESAY'V ATTORNEY United States Patent 3,537,054 GANGED POTENTIOMETER Edward H. Livesay, Ellicott City, Md., assignor t0 the United States of America as represented by the Secretary of the Army Filed June 11, 1968, Ser. No. 736,128 Int. Cl. H01e 13/00 US. Cl. 338132 1 Claim ABSTRACT OF THE DISCLOSURE Etched printed circuit cards containing individual resistors are easily removed by removing solely the shaft, which is continuous, from a ganged variable resistor bank. Each printed circuit card is individually removable and pluggable. The printed circuit cards have individual wiper arms mounted thereon, as opposed to being mounted on the continuous shaft. Defective resistors may be removed from a card without disassembling the entire ganged bank, merely by removing the card containing the defective resistor, the other cards remaining in place, after the shaft has been removed.

PRIOR ART There have been several different types of stacked resistors used in the past, prior to the present invention. One type was the stacked carbon or wire wound type variable resistor, which was unacceptable as it was not accurate enough, and the adjustment was not as close as desirable. Another type of ganged variable resistor, common in the prior art, utilized point-to-point wiring,

thus requiring a large amount of wiring, with the resultant problem that when any resistor on the switch deck was faulty it required the dismantling of the switch and desoldering of all wires up to the point of the band component. This dismantling required a substantial amount of time as the rotor for each deck of the switch was pinned to the shaft that served the complete switch. The problem with the prior art devices was the requirement of complete removal of the entire ganged resistor bank from the apparatus in which it was utilized before repair could be accomplished. Other disadvantages were that the removal of the pins and the reinstallation of them in the correct position often required more tools than were available to the average technician, and completely unavailable in the field.

The design of the present invention, employing etched printed circuit cards overcomes these problems by giving a desired connection between each resistor and a connector of the type shown in the drawings, for use in the connection to other points, thereby eliminating point-topoint wiring. Individual resistors, on the printed circuit cards of the present invention make it easy to locate and correct defects; this can be done more cheaply than in the prior art devices. As was previously mentioned, prior art devices require the dismantling of the entire unit to repair a defect, whereas in the present invention, the subcombination is still operable with the defective circuit card removed; moreover, repair may be accomplished on the individual components while the main ganged potentiometer unit still remains on the apparatus in which it is being utilized.

Typical prior art devices are exemplified by the devices shown in Pat. No. 2,748,230 to Burgess which issued on May 29, 1956 and Pat. No. 2,758,182 to Mucher which issued on Aug. 7, 1956. In the Burgess patent, due to interlocking, the entire ganged potentiometer unit must be removed in order to replace a defective sub-unit. This results since the components are not removable from the ganged potentiometer chassis while mounted on the apparatus in which the ganged potentiometer is being utilized; rather they are only removable as a unit. The shaft of the Burgess device is composed of interlocking sub-shafts, the shaft being removable only after the switch is dismantled, being held in place by a set screw. In the device shown in the Mucher patent, the wiper arms are mounted on the shaft rather than on the individual impedance components, as is done in the present invention. In order to remove a defective component, you must disassemble the entire apparatus up to the breakdown point by removing the nuts which hold the components in place. In order to do this, you must remove the entire ganged potentiometer unit from the apparatus in which it is utilized.

BRIEF SUMMARY The apparatus of the present invention overcomes the disadvantages of the prior art by utilizing preformed circuit cards, which are easily removable from a slotted chassis. Each of these preformed circuit cards is a completely independent sub-unit, having its own wiper arm mounted thereon for selecting a desired impedance value. A single, continuous shaft passes through the sub-units in order to lock the sub-units in place on the chassis of the ganged potentiometer and act as a common means for causing the wiper arms mounted on the individual subunits to rotate in unison.

The repair of defective components in the apparatus of the present invention is easily accomplished by removing the shaft, the individual sub-units still remaining in place, and then removing the defective sub-unit. The entire main ganged potentiometer unit can still remain on the apparatus in which it is being utilized, thus effectively greatly reducing the down time of the apparatus.

An object of the present invention is to provide a new and improved ganged potentiometer which overcomes the disadvantages of the prior art.

A further object of the present invention is to provide a new and improved ganged potentiometer having easily removable components.

A still further object of the present invention is to provide a new and improved ganged potentiometer utilizing preformed circuit cards.

Another object of the present invention is to provide a new and improved ganged potentiometer which is easily repairable.

Still another object of the present invention is to provide a new and improved ganged potentiometer which is easily repairable without removing the main unit from the apparatus in which it is being utilized.

Other objects and many of the intended advantages of this invention will be readily appreciated as the invention becomes understood by reference to the following description when taken in conjunction with the following drawings wherein:

FIG. 1 is a perspective cut-away view of the apparatus of the present invention, with certain components omitted for clarity.

FIG. 2 is a top view of the apparatus of the present invention, with certain components omitted for clarity.

FIG. 3A is an end view of the printed circuit card utilized in the apparatus of the present invention.

FIG. 3B is a front view of the printed circuit card shown in FIG. 3A.

FIG. 3C is a rear view of the printed circuit card shown in FIG. 3A.

Referring now to FIG. 1 which shows a perspective, cutaway view of the apparatus of the present invention, a plurality of preformed circuit cards 10-10, discussed in more detail below, are retained in a slotted chassis 11 solely due to retention slots 1212 located on opposite walls 14 and 15 of the slotted chassis 11, and retention springs 13-13, located on the front face of the preformed circuit cards -10, which resiliently force the card 10 toward the front of retention slot 12. The retaining slot 12-12, in conjunction with a plurality of connectors of the type shown in the drawings 16-16 having pluggable connector sockets contained therein, retain the plurality of the preformed circuit cards 10-10 in fixed alignment solely due to the retaining slots 12-12, the action of retention springs 13-13, and the pluggable connector sockets, which retain the card 10 due to a plug 17 of the type shown in the drawings mounted on the bottom thereof. The retention springs 13-13 perform the additional function of grounding the preformed circuit cards 10-10 to the slotted chassis 11. A single, continuous, slideable and removable keyed shaft 20 passes through the plurality of preformed circuit cards 10-10, interconnecting the cards so that Wiper arms 21-21 of the various preformed circuit cards 10-10 are driven in unison. The common keyed shaft 20 performs the additional function of locking the cards 10-10 in position on the slotted chassis 11.

The interconnecting feature of the common keyed shaft 20 can be more readily seen by referring to FIG. 2, which is a top view of the apparatus of the present invention. The preformed circuit cards 10-10, which in the preferred embodiment of the present invention are etched printed circuit cards, are maintained in a fixed alignment solely due to the retaining slots 12-12, the action of retention springs 13-13, and the pluggable connector sockets of the connector 16 of the type shown in the drawings located on the slotted chassis 11. Each of the plurality of printed circuit cards 10-10 is individually slideably removed in its associated retaining slots 12-12. The fixed alignment is independent of the presence of the individual printed circuit cards 10-10 so that, when one or more of the cards is removed (in order to repair a defective component, for example), the alignment of the remaining cards is still maintained. When the common keyed shaft 20 is removed from the apparatus, the printed circuit cards 10-10 may be easily removed from the retaining slots 12-12 if desired; thus, if any component should go bad it may be easily replaced by pulling the shaft 20 out through the cards 10-10, then removing the defective card 10 from the connector 16. This eliminates the desoldering of the wiring to other points in the chassis of both the ganged potentiometer and the apparatus in which it is being utilized. After the defective component has been replaced on the card 10, the card 10 can then be plugged into the connector 16 and with the key 22 on the shaft 20 mating with a key 25 on a hub 26 on the card 10, as shown in FIG. 3B, the shaft 20 is inserted through the card 10 in correct alignment. If desired, a new card 10 could be used instead of repairing the defective one as the cards 10-10 are completely interchangeable.

The wiper arm 21 or brush is mounted on the hub 26 which goes through a bushing 27 that is inserted in the printed circuit card 10, as is shown in FIG. 3A. When the hub 26 is inserted in the bushing 27, it will turn with ease. The hub 26 is held on the bushing 27 by a retaining ring 28. The wiper arm 21 will turn on metallic pads 29 of the printed circuit card 10, used for electrical connection to the impedance means, thus making it a complete unit in itself. A plug 17 of the type shown in the drawings is mounted to the bottom of the card 10 so it can be plugged into the connector 16 for easy removal.

A plurality of individual resistors 30-30 (shown in FIGS. 3A and 3B, but omitted from FIGS. 1 and 2 for clarity) are mounted upon each of the plurality of printed circuit cards 10-10 in a predetermined circuit arrangement for providing a variable impedance, an example of the preferred circuit arrangement being shown in FIG. 3C and generally indicated by reference numeral 31. The selection means, in the preferred embodiment being a Wiper arm 21, is mounted on each card 10 so as to rotate in a circular pattern about the common keyed shaft 20. Each of the wiper arms 21-21 is interconnected and 4 rotatively actuated by the common keyed shaft 20 so as to cause the plurality of printed circuit cards 10-10 to function in unison as an integral unit.

On the face of each of the plurality of printed circuit cards 10-10 containing the wiper arm 21, are metallic pads 29-29, each of which is electrically connected to one of the pulrality of individual resistors 30-30 mounted on the same face of the printed circuit card 10, in order to actually connect the wiper arm 21 to the desired impedance value. As can be readily be seen in FIG. 3B, the metallic pads 29-29 are mounted in substantially a circular pattern about the axis of rotation of the wiper arm 21. In the particular circuit arrangement 31 shown, the metallic pads 29-29 are mounted in two concentric circles about the axis of rotation of the wiper arm 21.

The required resistors 30-30 can be soldered into the cards 10-10 at preselected points 32-32, and checked before installation in the slotted chassis 11. Individual resistors 30-30 are soldered to the metallic pads 29-29 so as to form a series connection of the individual resistors 30-30, the series circuit being further connected to the pluggable connector 17 at selected tapping points designated by the numerals 35 through 39, inclusive, in order to yield the desired impedance value when selected by the wiper arm 21. As was previously mentioned, the printed circuit arrangement in the present invention is shown in FIG. 3C.

Summarizing the structure of the present invention, a slotted chassis 11 contains a plurality of slideably removable printed circuit cards 10-10, each card having mounted thereon a plurality of individual resistors 30- 30 in a predetermined circuit arrangement 31 and a wiper arm selection means 21 for selecting a desired value of impedance from the predetermined circuit arrangement 31; with connectors 16-16 mounted in a row on the chassis 11 for the desired number of printed circuit card 10 components. A keyed shaft 20 can then be inserted through the cards 10-10 so that the printed circuit card 10 components will function as a single unitary apparatus. -Etched printed circuit cards are utilized in the apparatus of the present invention, although other types of printed circuit cards come within the scope of this invention and may be utilized.

It is to be understood that the above-described embodiment of the invention is merely illustrative of the principles thereof, and that numerous modifications and embodiments of the invention may be derived within the spirit and scope thereof. Examples of such modifications are varying the type of preformed circuit cards utilized in the device, using a printed circuit card formed by depositing techniques rather than standard etch techniques and using thin film circuitry in place of printed circuits.

What is claimed is:

1. In a ganged potentiometer, a combination comprismg:

a plurality of preformed printed circuit cards, each card having a pluggable connector attached thereto and each card having a plurality of resistors upon each of said plurality of printed circuit cards in a predetermined circuit arrangement for providing the variable resistance;

a slotted chassis means including a plurality of retaining slots and a plurality of pluggable connector sockets for individually retaining said plurality of preformed circuit cards in fixed alignment solely due. to the retaining slots and the pluggable connector sockets, said plurality of preformed circuit cards being individually slideably removable in said slots, said alignment still being maintained when at least one of said plurality of preformed circuit cards is slideably removed;

a single continuous common slideably removable keyed shaft passing through said plurality of preformed circuit cards, for interconnecting said cards and locking said cards in position on the slotted chassis means solely due to said slideably removable keyed shaft;

a selection means mounted upon each of said cards for selecting a desired resistance value from the plurality of individual resistors wherein said selection means includes a rotating wiper arm rotatable about the common keyed shaft, said wiper arm interconnected by and rotatably actuated by the common keyed shaft for causing a plurality of printed circuit cards to function as an integral unit;

metallic pads mounted in substantially a circular pat-' tern about the axis of rotation of said wiper arm and on each of said printed circuit cards, each of said metallic pads being connected to at least one of said pluralityof individual resistors for electrically connecting said wiper arm to said selected desired resistance value, said resistors being soldered to said metallic pads so as to form a series connection for the individual resistors, said series circuit being further connected to said pluggable connector at selected tapping points in the circuit for yielding the desired resistance value when selected by the wiper arm;

and

a mounting means for mounting said selection means upon said printed circuit card comprising a hub, 21 bushing, and retaining ring for retaining said hub in said bushing, said hub being inserted in said bushing, and said bushing being inserted in said printed circuit card.

References Cited UNITED STATES PATENTS 2,303,499 12/1942 Rich 338-128 2,644,063 6/ 1953 Zikmund et a1. 200-468 2,670,422. 2/1954 Baum et al. 338-428 2,956,131 10/1960 Tabet 200-14 2,988,607 6/1961 Tabet 2 0011 3,013,152 12/1961 Webb et al. 33454 3,015,000 12/1961 Tabet 20014 3,015,755 l/196'2 Wright et al. 317101 3,221,114 11/1965 Hisao Maeda 20011 3,230,491 1/1966 Dreyfus et al. 338-134 X LEWIS H. MYERS, Primary Examiner A. T. GRIMLEY, Assistant Examiner US. Cl. X.R. 

